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July 5 1927.

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UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TOEDWARD F. COLLADAY, OF WASHINGTON, DISTRICT 0F COLUMBIA.

RADIO BROADCAST DISTRIBUTING SYSTEM.

Original application led October 28, 1924, Serial No. 746,357. Dividedand this application led Jnne 19, 1926. Serial No. 117,13L

My invention relates to systems of radio broadcast distribution, and thepresent application is a division of my copending applieation, SerialNo. 746,357, filed October 28, 1924, which is a continuation in part ofmy prior Patent No. 1,522,357. This invention has for its object toprovide an organization for the broadcasting of intelligence in whichorderly distribution may be secured. with maximum eiiiciency. The firstcharacteristic feature of the system is that of sending from each centerto the class or order of centers next below it without confusion andwith a minimum number of wave lengths. This is accomplished through theuseof double modulation, which also en. ables easy change of carrierwave frequency at the intermediate or relaying Stations.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a geographical diagram of the area of the United Statesdivided with respect to standard time, showing stations positioned toform part of a typical distributing system embodying this invention.

Fig. 2 is an enlarged geographical diagram of a. portion of Fig. 1showing subdivision of distribution in localized or districted areas.

Fig. 3 is a graphical diagram showing the channels of distribution andlines of authority and control in the system of Fig. 1.

Fig. 4 is a. circuit diagram of the same lsystem shown in Figs. 1 and 3.

Fig. 5 is a diagram of a telephone central station with two subscribersstations connected to it and is intended to be read with Fig. 5a.

Fig. 5a is a continuation of Fig. 5 and shows aradio central station anda radio suhscribefs station physically connected therewith through thetelephone circuits of Fiw. 5.

6 shows symbolically an arrangement of double modulating andtransmitting equipment at the A or master station of the system formatter originating there.

Fig. 7 shows symbolically equipment for the B stations, by means ofwhich the primary ca-rrier waves transmit-ted from the apparatus of Fig.5 may be demodulated and the intermediate frequency waves or envelopemodulated upon a new carrier wave C.

Fig. 8 shows symbolically'apparatus similar to that in Fig. 7, butintended to be located at the local or regional distributin stations C,receiving, therefore, on the wave frequency, transmitting on the D orsubscribers frequency.

Fig. 9 shows symbolically a subscribers set adapted to receive on the Dfrequency, to demodulate the short carrier wave, and then to demodulatethe intermediate frequency carrier wave, so as to produce audio waves asits output.

Fig. 10 is a. circuit diagram of the apparatus in Fig. 6.

Fig. 11 is a similar circuit diagram of the apparatus shown in Figs. 7and 8 which 1s the same in construction and arrangement, butditl'erently tuned accordino' to the station B or C, at which it islocated.

Fig. l2 shows symbolically a central office transmitting set which maybe located at A, B or C stations, any or all, for simultaneouslytransn'iitting the same modulations by means of a short singly modulatedcarrier wave, and a short double modulated carrier. The singlemodulation is intended for those outside the system while thedouble'modulation is distributed through the next lower order ofstations.

Referring to the drawings, and particularly to Fig. 1 this is a diagramof the United States of America, divided by lines t, t', and t2 intofour divisions marked respectively Eastern standard time, Central time,Mountain time, and Pacific coast time. It happens that the town ofHutchinson, Kansas, is within fifty miles of the geographical center ofthe United States and hence I have shown this town with three ringsaround it, and the letter A, indicating the location either of theheadquarters or master station of the entire system. In each divisionthere is one station with two rings around it, and marked B". These arethe head or master district stations of the several divisions, whichunder certain conditions vserve as relay stations between the A stationsand the other B stations for their respective divisions. Other stationsare shown in each division with one ring each, and marked B. These aredistrict stations, and receive either directly from the A stations or onoccasion by relaying from the head or master B stations in t eirrespective divisions. This illustrates the general manner ofdistribution, and will be referred to hereinafter.

Fig. 2 shows on an enlarged scale a portion of the eastern standard timedivision, which may be regarded as one or more districts, as it containsa number of district stations B. The main function of this'igure is toshow the relation between the district station and the local or regionaldistributing centers C. It is to be noted that IVashington, D. C., isthe head or master B station in the eastern division, while other townsfrom Boston to Augusta are shown in Fig. 2 with one ring as ordinarydistributing centers each serving a number (which in practice would bevery considerable) of outlying local or regional exchange centers markedC. Around each of these local stations or centers C are groupedsubscribers. These are not shown on Fig. 2, but are indicated in Figs. 3and 4, to which reference will presently be made.

In Fig. l, I have shown eight district stations B in the easterndivision, ten in the central division, and six each in the moun tain andPacific coast divisions, or a total of thirty. This of course isillustrative only and not to be taken as nal either in positioning ornumerical selection. As a matter of fact it the area of the UnitedStates be divided up into substantially equal districts, approximatelyone hundred district stations B would be a convenient number, but it isdoubtful Whether the traic would require this many district stations atfirst. In Fig. 2 I have shown a larger number of stations in part of thesame territory, as B stations, and have related a considerable number ofC stations thereto. The location of these is a matter of choice, andthey may or may not be associated with local telephone exchanges,

as convenience and traiiic conditions may demand.

For the purpose of a basic description herein of the system as a whole,in the simplest form, I shall assume that each of the three orders ofstations, B, C and D, is allotted a single carrier Wave frequency forreceiving, which is common to all the stations of the same order, andthat say ten intermediate or long Wave frequencies may be modulatedthereon, each intermediate frequency being in turn modulated at audiofrequencies intended for distribution. At certain times these tenintermediate frequencies may al1 be used at the master station A andbroadcasted on the B carrier wave to all the B stations, which in turnwill demodulate the initial carrier, amplify and reimpose the sameintermediate frequencies and modulations on the common C carrier waveand so relay them to all the C stations, which in turn will demodulatethe carrier waves received by them and reimpose the same upon the commoncarrier Wave alotted to all the D or subscribers stations. At othertimes there may be only one or two or even none of the intermediatefrequencies in use by station A and at such times the unusedintermediate frequencies may be allotted to different B stations or evento C stations for local or district broadcasting. In the iirst instance,it will be observed that the original modulations on all theintermediate frequencies are simply passed along by relaying until theyreach the' subscribers, who receive them in the original package, so tospeak, so that it is entirely possible to say truthfully to thesubscribers that they receive and actually hear the original audiomodulations, with equal eiiiciency from all points, foreign or domestic;and this in spite of the simplicity of their instruments.

Referring to Fig. 3, the station A is shown connected by lines ofdistribution to district stations B', B2, B3, and B4. The stations B arein the eastern division, the stations B2 in the central division, thestations B3 in the mountain division, and the stations B'1 in the coastdivision. Each of these district stations is shown connected by lines ofdistribution to local distributing stations C in its district, and eachof these local stations is shown connected to stations D typifying theultimate subscribers stations. The lines of distribution also representtelephone trunk lines from C stations to B stations, C represents thesubscribers telephone lines which either terminate in station C (if theyare identical with telephone exchange stations), or are connectedthereto, as indicated in Figs. 5 and 5a.

It will be noted that in Fig. 3 not all the' stations B are connected tostation A by direct individual trunk lines, but some district stationstrunk through a district master station, thus economizing trunk lines.Thus, the trunks 58, 59 and 60 in Fig. 3 are shown extending to masterdistrict stations in the groups B2, B3, and B4 respectively, other Bstations in these district groups being connected to A through therespective lnaster stations B by relatively short trunk lines 61. 62 and63. The number and routing of trunks so used is of course variable, andmay be accommodated to the necessities of telephone tratic so as not tointerfere with the normal telephonic use of the Wire plant, which is oneof the cardinal points in the design of the present system.

A better idea of the general'arrangement of circuits symbolized in Fig.3 is conveyed by Fig. 4, wherein a subscribers line 18-19 (see Fig. 5)extends from his station D to the central telephone exchange C which isequipped with line jacks J connecting plugs P-P and trunk jacks J 5.From the trunk jack J 5, shown in the figure, a trunk line 50 extends tothe district station B, which is also equipped with switchboardterminals including plugs P-PG and trunk jacks J 6, J 7. From the jack J7 shown in the figure a trunk 5l extends to the masterstation A where itterminates on a jack J 8. The station is equipped with plugs P7--P8, andmay be fully provided with telephone switching equipment, like thestations B and C. Details of such switching equipment are shown in Figs.5 and 5a, the parts being lettered the same in all figures. In Fig. 4,operators telephone instruments are shown at 83. connected in the usualmanner to the cord circuit, and these symbolize a complete signaling andsupervisory system. Each operator at stations B and A also has ademodulator and receiver for long IF waves, with suitable key forcontrolling the connection of the same to her cord circuits.

The radio equipment of station C includes a relay receiver andtra-nsn'iitter T with a local microphone and amplifier t2 for localmodulation. The ant-enna symbolized at 52 is supposed to receive wavessent out from the B station of the dist-riet in which the particularstation C happens to be located, and to which it is connected by meansof the trunk line 50, which of course does not symbolize all telephonetrunks but only such as may be allotted for the so-called radio traffic.The frequency to which the antenna circuit- 52 is tuned is that allottedto the C stations and to which tliey are all normally or permanentlytuned. The antenna circuit 53 is for radiating modulated carrier wavesto the subscribers D in the particular local area surrounding and servedby the station C under consideration. The frequency to which the antenna53 is tuned is that al.

lotted to the subscribers D, and to which they are all normally orpermanently tuned. The details of the subscribers station apparat-us,including both telephone and radiophone are shown in Figs. 5 and 5a,wherein a particular station of class D is designated as A', and will bedescribed hereinafter. Practically, while the subscribers stations maybe used as pickups, regular studio work will probably always be doneeither through PBX boards with special equipment, or in other specialstations connected with a C central station. All of these may be takenas symbolized by the station D or A' in Fig. 4. It should be noted inpassing that this allocation of original modulation to C stations doesnot interfere with direct broadcasting from A or B stations, since eachof these can most conveniently be located at and operated in conjunctionwith a telephone central exchange which is also a C station or has a Cstation connected to it, as

shown in Figs. 5 and 5a. Thus in Fig. 3 I have shown a microphonetransmitter 64 at every stat-ion of the orders A, B and C, to indicatethat broadcasting may be originated thereat when required. The actualmanner in which this is now intended to be done is shown in Fig. 4. Thesymbolic station C is provided with a pair of 'jacks J13 and J14 betweenwhich are connected the audio amplifier 65 and the intermediatefrequency modulator and oscillator transmitter 66. The jacks J13 and J14may be connected through the operators cords and plugs with the linejack J on the one hand and with either one of the jacks J 4 or J 5 onthe other. If jacks J8 and J13 are plugged together and jacks J4 and J14are plugged together, then the operation would be as follows: Assumingthe subscriber A to transmit sound waves electrically over his line18-19, these waves pass into the audio amplifier 65 and thence into themodulator 66, whereby a modulated intermediate frequency carrier wave iscommunicated to the input side of the relay transmitter T, which in turnmodulates the long wave thus produced upon the short carrier waveallotted to stations D, and radiates the same from the antenna 53. Thusthe stat-ion C is broadcasting on the common frequency wave, using anintermediate frequency which the subscribers can receive by doubledemodulation, in a manner to be presently described.

Now assume that instead of jacks J4 and J14 being plugged up together,the jacks J 5 and J14 are so connect-ed. The result will be as follows:The audio waves over line 18-19 pass to the audio amplifier 65 andthence to the modulator and oscillator transmitter 66, by means of whichan audio modulated intermediate frequency carrier current is transmittedover the trunk line 50 to the station B. At this station an arrangementof jacks is encountered similar to that at station C. Jacks J15 and J16have connected between them an intermediate frequency or carrieramplifier 67 which may be plugged up either for broadcasting from theantenna 55, or for continued transmission over the trunk 51 to thestation A. To produce the first result, jacks J 6 and J15 are pluggedtogether and jacks J 9 and J16 are plugged together. whereupon thecarrier current or intermediate frequency carrier waves will becommunicated to the inputcircuit of the oscillator transmitter B andthereby modulated on a high frequency carrier wave radiated from t-heantenna 55, at standard C frequency. This wave will be received and maybe relayed by all the C stations within range of the transmittingstation B. If wider distribution be desired the jack J16 is plugged ontothe jack J7 of the trunk line 5l, and the amplifier or relayedintermediate frequency carrier waves are transmitted to the station A.Here the arrangement of the intermediate amplifier 68 between the jacksJ 11 and J12 is the same as that of the amplifier 67 at station B. Byplugging up the jack J12 to the jack J1, the amplified intermediatefrequency waves will be communicated to the input side of the oscillatortransmitter T2 and thereby modulated on a short carrier wave andradiated Jfrom the antenna 57. As this Wave has a frequency allotted tothe B stations, all the B stations will receive it, and may in turnrelay it to the C stations and they in turn relay it to theirsubscribers. One reason for the rule that all broadcast matters shalloriginate at or through a C station will now be apparent, viz: that theinitial audio or telephone Waves may be changed as near as possible tothe point of origin to modulated intermediate frequency carrier Waves,which may then be imposed as modulations on a radiated carrier, or on aWire circuit, with equal eficiency. Audio Waves in a Wire circuit aresubject to distortion to a greater degree than modulated superaudiofrequency carrier waves. Also, by using superaudio frequency currents onthe trunk lines, advantage can be taken of the Well established systemsof multiplexing and relaying already in use, and the trunks renderedmore productive withoutinterfering with their telephonie use. Thus, theinitial audio waves are always changed into modulated superaudio wavesat the nearest central station, and thence dispatched either on acarrier Wave radiated from an antenna, or on a trunk wire to some otherpoint where they are so dispatched. In order to add still further to theflexibility of the system, the A station at the right of Figure 4 maytrunk as from a jack or jacks J1 through a trunk or trunks to any otherpart of the system, as for example to a particular B station, Where thetrunk may terminate on a jack similar to J, i'or connection t0 radiotransmitter T', or by further trunking to some particular C station, andso to the radio transmitter T at such station, whereby matter can bepicked up at any point and broadcast either generally or in a selecteddistrict or in a sclected local area only. It follows also from thisarrangement that when radio transmission is dillicult over longdistances or in any particular section of the system, due to seasonal ordiurnal or non-periodic phenomena, the distribution by Wire can be madeto supplement distribution by pure radio and the average of eliiciencymaintained throughout the system. To accomplish this every part of thesystem must cooperate perfectly with all other parts as determined bythe master control station A and district master control stations B, B',etc. both in time of transmission and maintenance of clear transmissionchannels. Such coordination may be compared to the system oftrain-dispatching on a railway system, and involves the use ofinterlocking records and time sheets, for A, B and C stations, and themanagement and dispatching of all radio trailic by a regular tratlicforce trained for that purpose.

Again referring to Fig. 4, it will be observed that station C as Well asstations A and B are indicated as having originating modulators (shownas microphones) 64, which may be plugged onto either the input side ofthe respective radio broadcast transmitters T. T and T2 or therespective trunks 50, 5l and the trunks from jack J9. At station C themodulating audio transmitter can be operatively connected to either jackJ4 0r J5 by inserting plug P in the jack J13 of the ampliiier and longwave modulator and oscillator 66, and then plugging jack J14 to eitherof the other jacks at will. The parts 65 and 66 are here made separateunits because they are common to all subscribers lines as well as theoperators microphone circuit. At station B the operators microphone isconnected to plug P1o through amplier 69 and long Wave modulator andoscillator transmitter 70; and at station A the operators microphone 64is connected to plug P11 through amplifier 71 and modulator andoscillator transmitter 72. At station B the trunks 50 bring in modulatedintermediate frequency (IF) Waves or carrier current, and in passingthis to either transmitter T or trunk wire 51, only amplification isneeded, which is supplied by unit 67, which may be a vacuum tube relayas Well as amplilier unit. Similarly at station A the trunks 51 from Bstations bring in carrier current or (IF) Waves, and a similar relay andamplifier unit is provided accordingly. Finally, to enable fullsupervision as Well as reception of audio at each station A, B and C,the operators circuits are indicated as provided with demodulators 72,74 and 76, and receiving telephones 73, 75 and 77 respectively. Theseare supposed to be connected to the cords through listening keysrespectively, which may also control the connection of ordinaryoperators telephones 81, S2 and 83, respectively, for telephoneconversation over cords, trunks and lines as usual.

It will be understood that Figs. 3 and 4 are merely outlines or skeletondiagrams, in which the metallic line and trunk circuits with all theirminutiae of line and cut oli relays, etc., are represented by singlelines, and the subscribers and central oice apparatus is all indicatedby elementary symbols; but are intended to represent fully developed andequipped standard lines and stations, as shown for example in Figs. 5and 5a. It may also be noted here that for simplicity of description andillustration I have purposely shown manual rather than automatictelcphone switching apparatus at the exchange centers, but for theattainment of every purpose and the performance of every function in mysystem which is herein shown attained or performed by manual apparatus,I contemplate as well the use of the corresponding automatic apparatus,as will be further explained hereinafter.

Referring to Figs. 5 ant 5, I have therein shown circuits of the centraloiiice and substation equipments and connections, Fig. 5 representingthe telephone side of the system, and Fig. 5u the radiophone side of thesystem. Before proceeding to detail description it may be noted that inaccordance with standard telephone practice, provision is made forkeeping the telephone lines and central oiice circuits clear of allgrounds or other disturbing connections during conversation. lVhen theradiophone goes into service, by closing the filament switch itsoperation in receiving is identical with that of any radio receiver, andin the event that use is made of any transmission of Waves over the linewires, as will be hereinafter pointed out, said transmission will be ata frequency above the limits of audition. In the present diagram, I haveshown the circuits arranged with nothing but continuous current forradio purposes over the telephone line wires. This is the simplest iormof control and the one nearest to present-day telephone practice, and isabsolutely certain not to produce any disturbance in adjacent conductorsin the telephone cables. Each radiophone set is provided with a cut olfrelay energized when the telephone set goes into commission, either bycalling or being called, and at the central otiice whenever the radiooperator takes control of the line, he disables it in the usual mannerby pulling up the cut ofi' relay at the telephone switchboard, thishowever being subject to the condition that a special tone test may beput on, so that all operators may know that the line is held on theradio board, and subject to interruption for telephone connection. Iprefer to use this tone test only with the radio operators testing plug,because his regular connecting plug includes within its functions thatof connecting a subscriber through the station amplitier to thebroadcasting transmitting set, and a connection of this character shouldnot be interrupted without permission.

Referring now to the diagram, Fig. 5, A and A are two subscribersstations connccted by line wires 16--17 and 18-19 respectively to thecentral station C where they terminate on jacks J .and J. 1:-1 are plugsforming the termmals of a cord circuit 20-21, 22-23, having a.bridgedrepeating coil I, ringing and listening keys, supervisory signalss--s and bridging connection to the main battery B. The same battery isshown supplying current to the line relays L, L and through contacts atthe cut off relays L2, L3 to the respective lines for calling purposes.In this system, when a subscriber takes down his receiver, the linerelay lights its lamp, which is extinguished when the operator insertsthe answering plug. Battery supply for the connected lines is thereaftertaken through t-he cord circuit 2U-22, 21-23, in a manner wellunderstood in the art. When the suhstation telephones are out ofservice, with their receivers hanging on their hooks, the line circuitsare conductively open for direct current, leaving the ringers Q, and Qin circuit for alternating ringing current passing through thecondensers g-g Referring now to Fig. 5a, it will be observed that theradio switchboard which l have designated generally7 by the letter It,is connected to the subscribers lilies by multiple taps marked 16, 17,and 18, and 18, 19, 19'). These terminate on multiple jacks J2, J3,corresponding to the multiple acks on the telephone switchboard. Itshould be noted that throughout this system the tip wires 16 and 18 withtheir branches are connected to ground, While the sleeve wires 17 and 19and their branches are connected to battery. This is extended into t-heradio side of the system for the purpose of securing proper balancebetween the main battery or power plant of that side and the mainbattery or power plant of the telephone side of the system.

At the subscribers stations taps are also taken of from the telephoneterminals t-o the radiophone terminals as indica-ted at 18C, 19C, and19". (The radiophone is shown only at one substation for sake ofsimplicity of illustration.) The two branches 19c and 191 are taken fromthe sleeve or battery side of the line 19, and are connected to oppositeterminals of the winding of a rela L4, which constitutes the substationcut o relay for the radiophone. The Winding of this relay is bridged bya condenser g2 through which both ringing and voice currents can passWithout substantial impedance. Where the radiophone is attached to aparty line substation, this relay L4 may be omitted, since on such partylines there are usually grounds on one side or the other. As willpresently appear, the radio circuits described herein are applicable totwo-party and four-party lines, with individual metering of the partystations.

Tormally, that is to say, when the telephone circuit is not in use, thecut oft relay L4 is deenergized and as a consequence the wire 19 isconnected through a back contact of the relay through extension wire 24to the branch 25 connected to the A battery marked A1 in Fig. 5a. TheWire 18c similarly passes through a back contact of the relay to theextension wire 2G leading to test or listening relay L5 and ground. 185,it will be remembered, leads to tlie tip or ground side of the line,therefore it is the side which in the radiophone can be made use of witha permanent ground or grounds, without disturbing the balance of thetelephone circuit.

The radiophone receiver at the substation A is shown as comprising anantenna 23, tuned coupler 29, lirst detector tube 30, tuned h'ltercoupler 33, second detector 3l, audio amplier tube- 32, and audiotransformers 34, 35, the last mentioned transmitting the amplified audiowaves to the telephone receiver or loud speaker 36. The ilamentbatteryis A1. The plate battery is B1 and suitable tuning condensers and coils,ticklcr coil for regenerative ei'ects, etc., are provided as required. Ishould remark in passing that this representation of the radio receiveris intended to be typical only.

The relay L5 has four pairs of contacts, one pair 275 closing the wires25 and 37 from battery A, to the lilaments. The second pair 275 closesthe wires 25 and 38 so as to put battery A1 on the telephone transmitterT, and through the induction coil I, to ground. The third and fourthpairs of contacts 27, 275, close the wires 39 and 40, forming terminalsof the secondary induction coil circuit, to the tip and sleeve side ofthe telephone line respectively, through the back contacts of relay L4.The transmitter T is shown hanging upon a hook switch H controlling theconnection of wire 42, constituting a parallel link between the batteryA1 and the filament bus 43. Thus the filament can be heated and theradiophone put in service either through the agency of the relay L5, orby the switch hook H. The former is controlled by the radio operator atcentral and the latter by the subscriber at the substation. In additionto the hook, the subscriber has a manual switch it by which he canconnect the battery wire 42 through a Wire 44 to his transmitter T, coiland ground, so as to energize his talking circuit. I provide an ordinarytelephone receiver t in series with the secondary of the induction coilI, and I interpose a pair of condensers g3,g4 between the secondary ofthe induction coil I, and the receiver t on the one hand, and theterminals of relay L5 on the other, so that while the subscriber bymeans of switch h can connect his phone '--t for receiving calls overthe telephone line, he cannot originate telephone calls thereover fromthe radiophone extension. This is subject to modification by omittingthe condensers if desired to originate calls.

Returning now to the central station, and

l particularly to the radio department thereof shown in Fig. 5, Trepresents a broadcasting transmitter, symbolized in very simple form,but supposed to contain the usual elements of power supply, modulator,oscillator and aerial, with suitable ampliiication of the audio wavessupplied on the input side. The jack J 4 connected to the amplifier t2and thence to the transmitter T, symbolizes a group of such jacks orequivalent connecting means such as automatic switches, controlled bydials or keys for connecting any of the wire lines to said radiotransmitter. Detailed appliances, both for the switching and for theradio transmission, are well known in the art, and need no speciicdescription.

The cord circuit between plugs P3 in Fig. 55 is the saine as theopera'tors cord circuit in Fig. 5, but the radio operator also hasspecial test cords such as that shown in the upper part of the figureconnected to plug I. Here the listening and ringing keys are of standardconstruction, as in the other cords, and the test contact of the plugl)4 is connected through suitable resistance to the supervisory lamp s2to the radio battery B, means such as the commutator p5 being providedto give special tone test on the test thimbles of the multiple jacks J,J, J 2, etc.

It will be observed that the constant connection of the sleeve orbattery wire 24 at the radiophone substation to the bus wire 25 of thebattery A1 produces charging of that battery by the constant flow ofcurrent therethrough from the main radio battery B at the centraloffice. The amount of energy thus delivered to the battery A1 dependsupon the size of the line wires, and the length of time available forsuch charging. As shown, the battery wire 24 is not cut oli' except whenthe cut olf relay L4 pulls up which is only when the line Wire is in usefor conversation.

Referring now to Figs. 6 to 9 inclusive, I have therein shown thearrangement of receiving and transmitting apparatus at the stations A,B, C and D of Figs. l, 2, 3 and 4. More particularly, these figuresconstitute a connecting link between Fig. 4 which is merely a skeleton,and the detail circuit figures which follow hereafter. Turning to Fig.6, I have shown therein an arrangenient of originating broadcasttransmitters at the head or master station A. The purpose is doublemodulation, by first inodulating by means of a telephone transmitterupon a long wave, and then modulating the long wave upon a short carrierwave of suitable frequency to be received at the stations B. It goeswithout saying, that this same arrangement of apparatus will be found ateach of the othercentral stations B and C, being indicated in Fig. 4 bythe numeral 6l. In order that this apparatus may also be employed forradio broadcasting of material brought into the stations over wiredtrunks, I show a jack J1 connected through an aniplilier to switchcontacts which may be connected through switch arms to the primary ofthe transmitter induction coil 302, the secondary of which is connectedto the modulator of the generating and transmitting set. Thus a trunkline or even a subscribers wire may be plugged on to the modulatorthrough the amplifier by means of jack J1".

Fig. 7 shows a relay apparatus primarily intended for use at. stations Band C, but which will also be used at master station A. Fig. 8 showsidentical apparatus.

The function of the apparatus of Fig. 7 is to take double modulatedwaves at the frequency allotted to the receiving station, de-

modulate the short wave carrier so as to produce modulated intermediatefrequency waves which are then passed through a tuned amplifier 305 to amodulator 306, by means of which they are modulated on a primary orshort wave carrier of a frequency suitable for the next lower order ofreceiving stations, in this case C stations. The short waves thusmodulated are then radiated.

By means of the jack 303, intermediate frequency or long waves modulatedmay be taken ofi' a trunk and passed through the amplifier 305 to themodulator 306 and thence radiated as before. Also, by means of the jack304 intermediate frequency or long waves modulated which have passedthrough the demodulator 307 and the amphfier 305 may be forthwith placedupon the wire trunk lines for transmission to other stations. Theseextensions should be available at each stage in the system, and Iconsider it original with me to provide means for affecting thesecombinations of superaudio frequency modulated waves transmitted eitherfrom wires to radio carrier or from radio carrier to wires withoutchange either in the intermediate frequency waves or in theirmodulations, and shall claim the same accordingly. This is one essentialfeature of the present system, which it is believed should be adhered toin any system of organized broadcasting, i. e. that when an originalmodulation is once made, the wave train carrying that modulation shouldbe preserved unchanged throughout 1t s entire course from point oforigin to the listeners receiver. As described herein, I accomplish thisby means of double modulation, with superaudio modulated waves modulatedupon the high frequency radio carrier. I shall presently show thatsingle modulated waves can be received and relayed with the sameultimate effect. I consider, however, that the method of doublemodulation is the best and most perfect for'this purpose.

Referring to Fig. 9, this shows typically a subscribers apparatus fortaking double modulated waves sent out from the stations of any of thereceding three figures, and demodulating t 1e same so as to recover theoriginal audio modulations and make them apparent. There are two units,one a demodulator of the short carrier wave, which produces the longintermediate frequency wave carrying the original audio modulations, andpasses these to the second demodulator, which demodulates theintermediate waves and passes the audio waves to the telephone receivershown at the right of the figure. This method is shown in detail in Fig. 5a at the subscribers station, where the circuit arrangement of sucha double demodulator is illustrated in full.

Fig. 10 illustrates the details of a circuit arrangement whichwillrealize the functions called for by Fig. 6. Primarily, of course,the purpose of this assemblage of apparatus is to produce doublemodulation of a primary or short carrier wave, that is to say, tomodulate a relatively long wave carrier, and then modulate this longwave upon a relatively short wave carrier which may conveniently beradiated in the usual fashion. Means for receiving and demodulating suchdouble modulated waves have been describcd in connection with Fig. 5aand will be further described herein. In Fig. 10, 150 is a microphonetransmitter in a local circuit 151 supplied with energy by battery B4and containing the primary winding of an induction coil 152, thesecondary of which is connected in the grid circuit 153 of the modulatortube 154, said circuit containing a battery Bi. The plate circuit 155 ofthe tube 154 is bridged by the power battery B and choke coils 157, andis connected through radio choke coil 157a, to the plate of the longwave oscillator tube 158. The plate circuit of the tube 158 contains a'battery B7, which battery is differentially connected to one coil of thecoupler 161, which in turn has a wire connection 160 back to the gridcircuit. The coupler 161 is tuned on its input side to the long wavefrequency supplied by the tube 158, and its secondary winding isconnected to the grid circuit of a second modulator tube 162, containinga battery B70. The plate circuit of the tube 162 is bridged by powerbattery B and choke coil 163, and is connected through the radio chokecoil 163a to the grid of the short wave oscillator tube 164. The platecircuit of this tube 164 contains a battery B1 and is connected througha condenser 167a and wire 167 to the antenna circuit, which is alsoconnected back to the grid circuit through wire 166. The antenna circuit57 is thus supplied with short wave oscillations modulated by the tube162 with long wave oscillations which in turn have been modulated by thetube 154 with audio modulations due to the primary modulator ormicrophone transmitter 150. It should be noted that this circuit is anadaptation of the I-Ieising modulator circuit in common use, and it isnot claimed herein, being shown for example on page 682 of the work onPrinciples of Radio Communication by J. H. Morecroft, published by JohniViley & Sons, New York, 1921. The use of this apparatus however incombination with other elements to produce theresults stated, and theadaptation of the circuit in question to the purposes of this system,are novel and will be claimed herein.

A modification of this circuit which permits general broadcasting bysingle modulation, and at the same time double modulation forbroadcasting` to subscribers, is indicated in Fig. 12. Here thetransmitter 150 is shown working through the induction coil 152 into themodulator designated generally as 154, the oscillator 158 and themodulator 162 into the short wave oscillator 164, all as per diagramFig. 10. The transmitter circuit 151 however, is branched through aswitch 151E to a second coil 1525, by which the same audio modulationsare repeated into the modulator 154a and thence into the circuit of theshort wave oscillator 164, in this Wa imposing the audio modulations dueto t e transmitter 150 directly upon the short carrier wave radiatedfrom the antenna circuit 57. This wave as it goes out will thereforecarry both long carrier wave modulations and audio modulations, and thelong carrier wave in turn will also carry the .same audio modulations.Receiving devices ot the ordinary type, adapted for single demodula--tion onl can receive the audio messages conveye in this way. By meansof the switch 1515 however, the operator can cut cti' the audiomodulator and restrict any part of the broadcast program to the doublemodulating circuit, for reception only by those who have doubledemodulating receivers.

The apparatus shown in Figs. 7 and 8 is intended to receive a doublemodulated carrier wave such as that radiated from the antenna in Fig. 6,demodulate the same and reimpose the long wave or intermediatefrequency, with its modulations, upon another short Wave carrier whichin the apparatus of Fi 7 as supposed 'to be the carrier wave of arequency allocated to stations C, while in the apparatus of Fig. 8 thisis supposed to be the carrier wave of a. frequency allocated to thesubscribers stations D. Glaneing at the four figures, (6, 7, 8 and 9),it will be observed that from the original modulation due to thetransmitter 150 to the final demodulation by the intermediate wave demodulator in Fig. 9, the same intermediate long wave carrier, and thesame audio modula'tions thereof, are maintained intact and unmodified,being merely passed along by relaying from station to station on shortcarrier waves, or as hereinbefore described on Wiredytrunk lines is theequivalent of the carrier waves.

The apparatus in Fig. 7 and that in Fig. 8 is identical except for thetuning of the transmitted carrier wave. The description of one thereforewill sufiice for both.

Referring to Fig. 11, which is a detailed circuit applicable to boththese figures, 54 is the receiving antenna coupled at 174 to the gridcircuit of the detector 170, whose plate circuit is connected through a.tuned filter coupler 175 to the grid circuit ot the amplifier tube 171,whose plate circuit is connected through the transformer 176 tothe gridcircuit of the modulator tube 172, which in turn has the usual Heisingconnections 178-179 to the circuit of the oscillator tube 173; the radiochoke coil 178, the power battery B14 and the magnetic choke coil 177being arranged as usual. The grid and plate of the oscillator tube 173are connected to the antenna inductance coil 180, which with the usualtuning condenser 180a is included in the antenna circuit 55. Filamentbatteries B11, B15, and B15 and plate batteries B12 and B16 are locatedas usual. As thus described, the assemblage constitutes a relay setwhich will take in the modulated long waves on a short wave carrier, andretransmit them on a carrier of different frequency, withoutdemodulating or disturbing the modulations of the intermediate or longWave. In order that these long Waves may be transferred from the firstdetector circuit to trunks and in order that modulated long wavesbrought in by trunks may be placed on the radiating antenna 55, Iprovide connections symbolized as jacks J 9-J 9. The jack J 9 has itssprings connected to the terminals of the coupler 175, and these springsnormally rest upon contacts in 'the plate circuit of the tube 170. Thejack 50 has its springs connected to the terminal of the coupler 17 6,and these springs normally rest on contacts connected in the gridcircuit of the modulator tube 172. Trunks such as 50 and 51 terminate onliacks J5 and J7, (see Fig. 4), adapted to be interconnected with eachother or with the jacks J 9 and J9 by plugs and cords as indicated at P5and P5. By plugging either one of the trunk jacks J or J7 onto jack J9,the corresponding trunk line will be connected to the tuned filtercoupler 17 5, whose windings are simultaneously disconnected from thedetector tube 170. Thus modulated carrier current at the same frequencyas the intermediate waves used in the radio side of the system, willcome over the trunk line 50, for example, through the jacks J5 and J9and plugs P5 and P5, and so to the coil 175, whence the long waves willpass to the grid circuit of the amplifier tube 171, to be amplified andthen sent through the modulator and oscillator circuits of tubes 172 and173. Any incoming trunk material can in this Way be put on the air atany station having the relay apparatus of Fig. l1

or the equivalent thereof. For reverse operation, by plugging either oneof 'the trunk jacks J6 or J7 onto the jack J9, the corresponding trunk,as 57 for example, becomes connected through plug P and plug P5 to plug.ISO and therethrough to the coil 176, whose primary winding issimultaneously disconnected from the grid circuit of the modulator tube172. The incoming modulated short carrier waves received on the antenna54 will pass through the detector 170 and by demodulation of the primarycarrier long intermediate frequency waves will be passed through thefilter coupler 175,

amplified by the tube 171, and so communicated through the coupler 176to the cord circuit and jacks, directly to the trunk line 51. In thisway, material can be taken off the air at any time and put on the trunksby simply obliterating the primary carrier wave. It is to be understoodthat by varying the tuning of the couplers, long waves of any frequencycan be taken from or fed onto the trunks.

The general operation of the system thus described will now beunderstood. Ordinarily, items collected, through the system would comeinto A over the wire trunks and if of general interest, would be passedthrough from a trunk such as 50 in Fig. 1.1 to the jack J9 and thencethrough the amplifier, modulator and oscillator to be radiated. Thisradiation would be in waves of B frequency, and Without otherdistinctions would be picked up by all the B stations, or at least thehead B stations, for relaying, as by their apparatus shown in Fig. 7, tothe C stations and thence by means of'theii` relay apparatus such asthat s hown in Fig. 8 to the subscribers. In practice there will be adivision of such broadcasting, as to items of importance, so as to givethem their proper time of distribution in the several divisions of theterritory.

As a matter of expediency, the compromise method of regulating the timeof a performance of any kind so that it may be broadcasting in all thedivisions simultaneously will probably be practiced until the public hasbecome accustomed to an organized system.

The foregoing description, While addressed primarily to broadcastingfrom station A, includes items drawn from different parts of the system,which implies transmission through B stations from C stations, either bywire or by radio. Matters originating at station A are handled by meansof the apparatus of Figs. 6 and 10 but may' also be handled by plugging.the transmitter 64 (Fig. 4) with its amplifier 7 2 and intermediatefrequency modulator and oscillator 7l on'toa trunk or trunks 51 leadingto B stations, from which the actual broadcasting can be done byconnecting trunks to their intermediate Wave amplifiers and themodulators and oscillators of their short carrier waves. (See Figs. 4and 11.) In other Words, the station A can either broadcast direct or byWire trunking through the B stations, preferably the head B station ofeach division. It is further to be noted that the A station when soworking over wire trunks can receive the same waves radiated from B orantenna 56 (Fig. 3) and by demodulating and listening to the audiofrequency component thereof can determine the eihciency of transmissionand the timing of the B apparatus with respect to the short carrier waveemployed.

Each station B is supposed to be a district station, that is, itcompiles and checks up all bookings or regular number items in itsdistrict, keeps the A station informedthereof, makes up districtprograms, supervises local or C programs including items to be recordedand released later, receives, records and forwards traffic reports andcharges from its district to A and acts as a relay station for mixedwire and radio transmission between the C stations in its district andthe rest of the system. First, however, the functions of the C stationsshould be fully understood. These are the stations which come intoimmediate contact with the subscriber, and which for transmissionpurposes form their immediate source of supply. So far, as the generalbroadcasting goes, these stations will be largely considered as they aredescribed in my Patent No. 1,522,357, viz: as relay or distributingstations, each for its own local area. In speaking generally of 'thesestations it will be understood that they may or may not be identicalwith the telephone central stations for the same areas. In the majorityof cases each radio C station will be one of a group of telephoneexchange stations in its area, and will receive communications from allparts of the area except its own particular territory, by trunking. Thefunctions of each radio exchange C include the following: Relaybroadcasting on the subscribers or D carrier wave frequency of programitems originating at B or A stations; selection of items and arrangementof local programs to include approved local items if any; listening inand supervising reception by subscribers, using the wire lines for thispurpose; connecting subscribers wires or studio wires to trunk lines fordirect communication or preferably through amplifier modulator andtransmitter units 65 and 66, for superaudio carrier current transmissionover trunk lines 50 or to iocal broadcasting transmitters T as indicatedin Fig. 5a; and com iling, editing and publishing in the press, y wire,and otherwise, the radio pro rams for the local area served.

Relay fliroadcasting by the C stations would ordinarily be done by meansof the apparatus symbolized in Fig 8, which is adapted to doublemodulation.

For listening in and supervising reception by the subscribers, the radiostation C makes use of the apparatus shown in Fig. 5, whereby the wavesradiated from the transmitting station may be caused to return afterdemodulation over the wires so as to be audible to the operator througha proper listening apparatus. The apparatus of Fig. 5a also includeselements such as V, P4, etc. for testing the subscribers line andinstrument. If local batteries are employed at the subscribers stations,their condition and voltage can be ascertained and if all current issupplied from central as in my prior applications, Serial No. 699,023,filed March 13, 1924, and Serial No. 722,993, tiled June 28, 1924, thenthe resistance of the circuits and their proper tuning can be determined.

For connecting subscribers wires or studio wires to trunk lines fordirect or telephonie communication the radio operator has cord circuitsand terminals of the lines, symbolized at P3, J3, J2, etc., in Fig. 5aand may have equivalent automatic or semiautomatic switching apparatus.The operation is symbolized in Fig. 4 which shows jacks J and J 5 bymeans of which the subscriber A can be trunked to any part of the systemwithout going through the telephone switchboard. The typical andpreferred mode of trunking by wire in this system, however, is by meansof modulated superaudio frequency carrier current which can beinterchangeably imposed on the wired circuits or upon suitable radiofrequency carrier waves so as to render transmission and interchangeover and between the elements of the mixed system both simple andflexible. rThis is accolnplished by first of all modulating thesecondary intermediate frequency in accordance with the sounds which itis desired to transmit; and then sending this modulated carrier currentover the trunk circuit or circuits to the point where it is to beutilized. Thus, for example, in assuming a trunk connection from thehead B stations in Fig. 1 to the master station A, it is taken forgranted that the wire trunk lines em loyed for this purpose may bemultiplexed1 and provided with tube relays and amplifiers, the same asat present. If more than one intermediate frequency is assigned to theradio broadcasting corporation for use on wired trunk lines, all suchfrequencies of carrier current might be confined by agreement to thesame trunk or trunks, or if a more exible agreement were possible, itmight be applied over any trunks in the system. This is not to beconfused with telephone trunking broadly, even though it be employed fortransmitting sounds from a distance to a radio broadcasting studio. Thecombination I present is more flexible than that, and at the same timemore comprehensive, because it includes all the elements of an organizedsystem, whereby modulated intermediate carriers may be forwarded eitherby means of wires or by means of double modulated carrier waves, fromany point in the system to any other point in thc system, without lossesor distortion due to changes in frequency or tuning. It will beremembered that for receiving purposes the instruments at suhscribersstations are all supposed to be standardized, and tuned to one fixedfrequency. (This of course is subject to distribution of carrier wavefrequencies as expediency may determine and as recommended by theGovernment. For general purposes it may be assumed here that allsubscribers instruments are tuned ixedly for the same primary carrierwave frequency.) In passing through the relay stations however, theprimary carrier wave frequencies change from A to B, from B to C, andfrom C to subscribers D. Thus, if the sending station B should vary thefrequency of the C carrier wave transmitted, this would not atleet theintermediate wave frequency or the audio modulations, and so long as Cuses the proper frequency D, for the subscribers, the originalintermediate waves formed and modulated at the point of origin, would beavailable in the subseribers tuned local cir.

cuit, the second detector circuit shown in Fig. 5a. On the other handsuppose there be variations in the carrier frequency employed by C inbroadcasting to the subscribers station D the subscribers station isshown provided with means to tune the antenna circuit as well as theinput circuit of the first tube. Thus the variation in primary carrierwave frequency sent from C could be compensated, but the intermediatewave frequency and the audio modulations thereon are unaffected. As amatter of convenience, subscribers instruments may all be tunable withina certain band of frequencies, to ofi' set any momentary irregularity orvariation in transmission wave length from C, as well as to permitreception of single modulated waves. In making use of intermediatefrequencies, both by trunking and by double modulation of primarycarrier waves, it is therefore important that t-he intermediate wavefrequencies be maintained constant and exact throughout the system. Forthis purpose, a part of every program should be sent out from station Aor at certain xed times, a tuning wave of master frequency should besent out throughout the entire system from station A, preferablyearrying a definite audio signal to identify it. Such transmission ofstandard tuning frequencies is already practiced in respect of pureradio waves, by the Bureau of Stand- IUC ards at VVasllington, D. C.,and it has been proposed by the commercial companies also to transmitstandard frequency radio Waves from a master station to subsidiarystations, in order that distribution of frequencies may be accomplishedby means of harmonics taken therefrom. I do not know however of any useof an intermediate frequency master 4 wave distributed over a system,particularly a mixed system of wire and radio links, for tuningpurposes. I believe therefore that this is original with me and shallclaim the same accordingly. Further than this, inasmuch as modulation ofintermediate frequencies may take place at the B stations or even at theC stations by the use of modulator 64 in Fig. 4 or the circuit of Fig.10, and as there Will .be many of these stations throughout the system,with a corresponding possibility of error, it is to be particularlyunderstood that I contemplate the use of the long or intermediatefrequency master wave sent out from station A for the purpose ofcalibration or tuning to resonance therewith of all the long Waveoscillator circuits 159, 160 and 161 of Fig. 10, or their equivalents."As a matter of fact, the tuned filter coupler 161 will be calibrated bymeans of this master wave. A convenient method of doing this is toreceive the short Wave carrying the master long Wave on the antenna of adouble demodulating receiver test set and the long wave from theoscillator 158 adjusted 1n frequency by tuning its circuit to givemaximum sharpness in the receiver of the test set. Thus the circuitsshown in Fig. 10 can be used for calibration throughout the system witha master tuning Wave sent either over the Wired trunks or by pure radiothrough the ether. In either case the pitch or frequency of the longwave transmitted will be identically the same; and its distribution overthe system may follow the same channels as any other broadcasting, viz:by pure radio from A to B, relayed A from B to C, and again relayed fromC to D to Atest out the subscribers circuits. Any dissonance detected inthe last link between C and D, would be reported at once, as Suthcientlyserious to rece-ive immediate attention, because all tuning forintermediate fre- %uency or long Waves should be definit-e and Xed inthe receivers, and therefore any variations must be taken care of at thesending stations. This has nothing to do 'with the antenna. I considerthis method of calibrating and tuning` a system to be original with meand shall claim the same accord ingly.

As an alternative method, I may permanently impose the master long waveat superaudio frequency on all the relay stations through the trunks, toexcite oscillator or more correctly amplifier tubes so as to produceintermediate frequency or long Waves,

Which may then be modulated, an'lplified` and transmitted in the mannershown herein or any other desired or suitable manner. To accomplishthis, the only change in the circuit of Fig. 10 would be to disconnectthe grid circuit from the plate circuitof the long Wave oscillator 158,and connect said grid circuit through a suitable tuned filter coupler tothe trunks carrying the master Wave. The tube 158 will then becontrolled as to its frequency of oscillation by the master Wave. Inthis Way a master frequency sent out through the system by either longWaves over the trunks, ordouble modulated short Waves through the ether,can be used permanently to excite and regulate every long Wavetransmitter or generator in the system. As described, the B stationswould relay the master Wave on a short Wave carrier to the C stations,maintaining this service constant While the program was in force, but ifthe master long wave be transmitted over wire trunks, then of course tothat eX- tent the Wire trunks would be in permanent use for radio. Thismode of actuating transmitter generators in synchronism by a distributedmaster Wave applies not only to the circuit of Fig. 10 but to any andall of the oscillators disclosed in the system, the frequency of themaster Wave being determined according to the desired frequencies ofoscillation in the transmitting tubes. I consider this method and typeof apparatus for practicing it to be original with me and shall claimthe same accordingly.

Coming to the subscriberis station, the primary Wave frequency which herecelves is fixed, but referring to Fig. 5a it will be observed that thefilter coupler 33 shown between his first detector 3() and seconddetector 31 is provided with variable. tuning elements, as are also hisantennna circuit 28 and his local input circuit 43. The subscriber maytherefore select intermediate frequencies by merely tuning his filtercircuit 33. In tuning, both sides must match up as Well understood bythose skilled in the art. Thus, initial distribution by station A onseveral frequencies simultaneously results in selection at station B andrelayin of the selected items, plus addition of original items, onseveral frequencies, all of which afford station C the opportunity ofselection plus the addition of original matters, for relaying andtransmitting to the subscribers D; while the subscribers in turn bytuning their intermediate Wave filter circuits can select any and all ofthe items desired and reject the others. It is of course possible forall the modulated frequencies at A to be relayed from B to C and from Cto the subscribers, using Whatever number of primary frequencies andintermediate frequencies are available. This might actually occur when anational program lul) was being carried on which must be condensed inpoint of time, requiring the transmission of several items at once, fromwhich the ultimate subscriber must 'select those which he would preferto hear. I consider this arrangement and the method of operating relaystations in an organized system for purposes of selection of program tobe new and original with me and shall claim the same accordingly. Thisapplies as well to subscribers stations as to the intermediate and Astations, and to the entire system as such.

It is of course understood that any or all of the details, constructionand operation thus outlined, may be changed and modified as necessity,convenience, and the resources of the art from time to time may dictateor permit, without departing from the .scope and purview of myinvention. I believe I have disclosed a complete and operative systemfor the purposes described, which is lit) novel in totality, as well asin its several divisions and parts, and that the methods employedthroughout are novel, when considered in an organized system. I do notclaim the specific circuits shown except as hereinbefore stated, but Ido claim the system of the parts and the method of operating the same,as herein disclosed and I wish it distinctly understood that Icontemplate all non-essential changes and modifications which may bemade therein.

iVhile the master station has been described as being located near thegeographical center of the system, it may be permanently or at timeslocated in any division, for example, at New York in the easterndivision, controlling other divisions by wire or by radio relayingrepeated from division to division. The master station. whereverlocated, is for the time being the center of the system.

What I claim is:

1. The combination with a general organized wire distributing systemhaving a plurality of subscribers stations, of a radlo broadcasttransmitting station. a plurality of first and second order relaystations, means at the broadcast transmitting station for transmittingsignals on a double modu'- lated wave, means at each said first relaystation for receiving said double modulated wave and retransmitting theintermediate wave thereof on a second radio carrier wave, means at eachsecond relay station for receiving said second carrier wave andretransmitting the sai-d intermediate wave borne thereby on a thirdradio carrier wave, and radio receiving means at the subscribersstations arranged to receive and double demodulate said third radiocarrier wave, individual wire connections between said second relaystations and the subscribers stations served thereby, trunkingconnections between said first mentioned broadcast transmitting stationand the said first order relay stations and trunking connections betweensaid first order relay stations and said second order relay stations,whereby signals station to said subscribers stations each on fixed radiocarrier wave frequencies allotted permanently to the receiving means ofthe station next below it.

3. In a syst-em of the class described, a plurality of broadcastingstations arranged in classes in order of transmission for re-y laying bystages, the stations at each stage being increased in number over thoseof the preceding stage, means for initially modulating a superaudiofrequency carrier wave or carrier current, suitable for transmissionover wired circuits, with means for modulating this long wave orintermediate frequency upon a short wave of high frequency suitable forradio transmission, means at each relay station in the system todemodulate the short waves and remodulate the intermediate frequencywaves on a different short wave carrier, and subscribers receivingstations equipped with means for demodulating both the short carrierwave and the long intermediate wave, to take off the audio ,signals 4.In a system of the class described, a plurality of broadcasting stationsarranged in classes in order of transmission for relaying by stages, thestations at each stage being increased in number over those of thepreceding stage, means for initially modulating a superaudio frequencycarrier wave or carrier current, suitable for transmission over wiredcircuits with means for modulating this long wave or intermediate frequency upon a short wave of high frequency suitable for radiotransmission, means at each relay station in the system to demodulatethe short waves, and means to transmit said intermediate frequency wavesthus taken off, in the form of amplified carrier current, over wires toother stations.

5. In a system of the class described, a plurality of broadcastingstations arranged in classes in order of transmission for relaying bystages, the stations at each stage being increased in number over thoseof the preceding stage, means for initially modulating a superaudiofrequency carrier wave or carrier current, suitable for transmissionover wired circuits, with means for niodulating this long wave ofintermediate frequency upon a short wave of high frequency suitable forradio transmission, means at each relay station in the system todemodulate the short waves, and transmit said intermediate frequencymodulated waves as amplified, carrier current over wires to otherstations, together with means at such receiving stations to receive saidmodulated llong waves and to amplify and remodulate the same upon shortcarrier waves and retransmit them by pure radio.

6. In a combined radio and wire system, a plurality of transmitting andreceiving stations having both radio and wire apparatus, and means tomodulate long waves and to interchangeably transmit the same over saidwires or as modulations on short carrier waves.

7. In a combined radio and wire system, a plurality of transmitting andreceiving stations including local or regional broadcasting stationshaving both radio and wire apparatus, and means to modulate long wavesland interchangeably transmit the same over said wires or as modulationson short carrier waves, together with subscribers stations equipped withreceiving means and wire connections to the local or regionalbroadcasting stations.

8. In an organized wired signaling system having a pluralit of groups ofsubstations, the substations o each group being connected by wire to aservice station common to the group and provided with radio receivingmeans connected to the service station over said wire connection forsupervision therefrom, and means for transmitting by double modulation acommon signal modulated intermediate frequency wave modulated on,different carrier waves over a common area.

9. A combined organized wire system and organized radio systemcomprising means for producing a signal modulated wave of intermediatefrequency, interchangeable means for distributing said intermediatefrequency wave by wire and as a modulation on a radio carrier wave tosubscribers receiving stations, double demodulating radio receivingmeans at said receiving stations arranged to detect and demodulate saidintermediate frequency wave, whereby only such persons as are providedwith such double demodulating receiving sets may detect lui saidintermediate frequency wave, and means for independently and at will,broadcasting the same signal carried by the intermediate frequency waveas single modulations on a radio carrier wave whereby the signal may bemade available for receiving instruments outside the system.

10. The combination of an organized radio broadcasting system with anorganized wire communication system comprising aI plurality ofsubscribers stations D grouped in local areas, a local distributingstation C for each such area, district rela stations B related to groupsof stations (il and a master station A related to all the stations B,radio broadcast transmission proceeding from the master station outwardthrough the relay stations B to C, and by relay distributing from C toD, all of said stations being provided with modulating radiotransmitters for broadcasting original matter, means in each local areafor connecting the subscribers stations D to the local broadcastingstation C through circuits of the wire system, wire trunk circuitsconnecting the distributing station C to the district stations B, andother wire trunk circuits connecting said district B to the masterstation A, with means at each station A, B and C to receive doublemodulated carrier waves, with relay transmitters at each of the stationsB and C comprising means to demodulate the primary carrier wavereceived, means for amplifying the intermediate frequency modulationwave, and means for modulating the same upon another short primarycarrier wave for transmission at a different frequency from that of theprimary carrier wave received.

11. In an organized system of radio broadcast distribution, means fortransmitting double modulated carrier waves to receiving stations infixed tune, means for independently transmitting a master wave of exactintermediate frequency over the system, and means to synchronize thetransmitted inter-l mediate frequency therewith.

12. In an organized system of radio broadcast distribution, a pluralityof means for transmitting double modulated carrier waves to receivingstations in fixed tune, common means for independently transmitting amaster wave of exact intermediate frequency over the system, and meansto synchronize the transmitted intermediate frequency therewith.

In testimony whereof I hereunto aix my signature.

EDWARD E. CLEMENT.

